The present invention relates to lasers, and particularly to a control system for high-power lasers. The invention is particularly useful for the high-power laser described in U.S. Pat. No. 4,486,887, and it is therefore described below for purposes of example with respect to such a laser.
U.S. Pat. No. 4,486,887 describes a high-power flowing-gas laser, in which the laser channel is folded to include at least two, and preferably four, legs angularly disposed to each other in a common plane and having a single folding mirror between the two legs. The construction is such that the laser rays passing through one leg, on the upstream side thereof with respect to the gas flowing transversely across that leg, are reflected by the folding mirror so as to be transposed to the downstream side of the other leg with respect to the gas flowing tranversely across the other leg. Such an arrangement provides compensation for phase distortion due to the density gradient, for velocity variations due to the turns in the flow, and for amplitude variations due to the gain gradient, in the gas flowing transversely across the legs of the folded channel.
However, the resonator cavity in such a laser may be somewhat unstable, resulting in a deviation of the outputted laser beam from a desired reference position.